Manifold Pressure/Vacuum Sensor: Testing and Inspection

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR DIAGNOSIS

CIRCUIT DESCRIPTION
The manifold absolute pressure (MAP) sensor responds to changes in intake manifold pressure which gives an indication of the engine load. The MAP sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit. The powertrain control module (PCM) supplies 5 volts to the MAP sensor on the 5-volt reference circuit and provides a ground on the low reference circuit. The MAP sensor provides a signal to the PCM on the MAP sensor signal circuit, which is relative to the pressure changes in the manifold. With low MAP, such as during idle or deceleration, the PCM should detect a low MAP sensor signal voltage. With high MAP, such as ignition ON, engine OFF or wide open throttle (WOT), the PCM should detect a high MAP sensor signal voltage. The MAP sensor is also used in order to calculate the barometric pressure (BARO) when the ignition switch is turned ON, with the engine OFF. The BARO reading may also be updated whenever the engine is operated at WOT. The PCM monitors the MAP sensor signal for voltage outside of the normal range. If the PCM detects a MAP sensor signal voltage that is excessively low, DTC P0107 sets. If the PCM detects a MAP sensor signal voltage that is excessively high DTC P0108 sets.

DIAGNOSTIC AIDS
Poor idle characteristics may be caused by uncontrolled fueling due to an open or high resistance in the HO2S 1 low signal circuit. Before replacing any component, ensure that this condition does not exist.

TEST DESCRIPTION

Steps 1-6:

Steps 7-14:

Steps 15-22:

Steps 23-31:

The number below refers to the step number on the diagnostic table.
4. This step tests the MAP sensor's ability to correctly indicate BARO.
12. The measurement noted in this step will be used in subsequent steps if the measurement does not exceed the specified value.
15. This step calculates the resistance in the 5-volt reference circuit.
16. This step calculates the resistance in the low reference circuit.